* The Onix line is the only one which can be completely acquired with [[List of in-game trades|in-game trades]]. However, this is only possible in {{game|HeartGold and SoulSilver|s}}, in which the player can trade {{p|Bellsprout}} for Onix in [[Violet City]], any Pokémon for Steelix in [[Olivine City]].

* The Onix line is the only one which can be completely acquired with [[List of in-game trades|in-game trades]]. However, this is only possible in {{game|HeartGold and SoulSilver|s}}, in which the player can trade {{p|Bellsprout}} for Onix in [[Violet City]], any Pokémon for Steelix in [[Olivine City]].

Biology

Onix resembles a giant chain of gray boulders that become smaller towards the tail. There is a rocky spine on its head and a pair of black eyes right beneath it. This Pokémon has a magnet in its brain that serves as an internal compass. Its body absorbs many hard objects, making its body very solid. As it grows older, it becomes more rounded and smoother, eventually becoming similar to black diamonds.

Onix tunnels under the ground at over fifty miles per hour, which causes tremors and a terrifying roar that echoes a long way. The massive, winding tunnels it leaves behind are used as homes by Diglett. Onix loves to eat the large boulders it encounters while burrowing underground. As seen in the Pokémon Stadium series, Onix is capable of rotating its head, or any part of their body, a full 360 degrees. It is a very aggressive Pokémon that will constantly attack humans and Pokémon when it is in pain, as seen in the anime. Onix can be found in mountains and caves, though it prefers underground tunnels with little light.

The Crystal Onix featured a special Onix whose body is made out of glass crystal. Ash and his friends helped a glass sculptor named Mateo search for it because Mateo believed it would help inspire him to be better at his craft.

A "King Onix" was featured in Hooked on Onix. Team Rocket tricked King Onix into thinking Ash and his friends were going to destroy his kingdom. When Ash managed to convince King Onix that he and his friends weren't bad by defeating it in a battle, Team Rocket tried to steal the royal Rock Snake Pokémon, but their plan was foiled, as usual.

In the TCG

Other appearances

Onix is obtainable in a Poké Ball. Once thrown, it flies up into the sky and uses Rock Throw on the player's opponents. This will hit everyone on the field except Kirby if he uses his down special move.